1. Field of the Invention
The present invention relates to a gas analyzer for simultaneously measuring many ingredients in a gas and which is adapted to be able to simultaneously measure at least two kinds of ingredient gases contained in a sample gas. In particular it provides a novel gas analyzer for simultaneously measuring many ingredients which can meet the requirement of simultaneous and high accuracy measurement of the concentration of a high-concentration ingredient gas and that of a low-concentration ingredient gas in a sample gas comprising a mixture of the high-concentration ingredient gas and the low-concentration ingredient gas. Such a gas analyzer has heretofore been considered difficult to achieve.
2. Description of the Prior Art
A gas extraction type metal analyzer for measuring the quantity of various kinds of impurities contained in a metallic sample and the like has been known, and is a gas analyzer which can simultaneously measure many ingredients and in so doing can simultaneously measure at least two kinds of ingredient gas.
This gas extraction type metal analyzer is, as shown in FIG. 6, comprised of a gas extraction portion 0A and a gas analyzer portion 0B connected to said gas extraction portion 0A for simultaneously measuring a plurality of ingredients, e.q. two ingredients. Said gas extraction portion 0A is comprised of a heating furnace 01, for example a graphite crucible, for driving off various kinds of ingredient gas, such as CO gas, N.sub.2 gas, H.sub.2 gas and the like, corresponding to various kinds of impurities such as oxygen, nitrogen, hydrogen and the like, contained in the metallic sample by heating the metal sample to melt it in the presence of a carrier gas, e.q. an inert gas such as He gas, fed through a carrier gas-introducing passage 00. An electro-magnetic purge valve 02 is connected to the outlet of the furnace. Said gas analyzer portion 0B for simultaneously measuring a plurality of ingredients, in this embodiment two ingredients, is comprised of a pressure regulator 04, a flow control needle valve 05, a first gas concentration detector 0D.sub.1 for measuring the concentration of CO gas, which can be, a non-dispersion type infrared detector, an oxidizer 06 for oxidizing CO gas and H.sub.2 gas contained in the sample gas which has passed through said first gas concentration detector 0D.sub.1, to turn the CO gas to CO.sub.2 gas and the H.sub.2 gas to H.sub.2 O gas, respectively, a CO.sub.2 -remover 07 for removing CO.sub.2 gas by a chemical reaction between it and a CO.sub.2 -removing agent, a H.sub.2 O-remover 08 for removing H.sub.2 O gas by a H.sub.2 O-adsorbent, a second gas concentration detector 0D.sub.2 for measuring the concentration of N.sub.2 gas in the sample gas, which detector can be a heat conductivity type detector, and an exhaust passage 09 connected in series in the recited order. The gas analyzer portion 0B is connected to the gas extraction portion 0A through a sample gas-introducing passage 03, which is connected with said electro-magnetic purge valve 02 of said gas extraction portion 0A. However, such gas analyzer portion for simultaneously measuring a plurality of ingredients having the conventional construction used in the above described gas extraction type metal analyzer has shown the following various disadvantages. With the conventional gas analyzer, for simultaneously measuring a plurality of ingredients, since the measurable upper limit is at most several thousands ppm, only small quantities of various kinds of impurities contained in the metallic sample can be accurately measured. Also, even where a comparatively large amount of various kinds of substances are contained in the sample, if these various kinds of substances are not present in greatly differing quantities, the gas analyzer can in practice be used without any problem only by suitably diluting the sample gas obtained from the sample.
However, recently it has became increasingly important to be able to simultaneously analyze ceramics and the like for many ingredients, such as the principal ingredients and impurities, such as Si.sub.3 N.sub.4 having a large amount, such as of several tens %, of nitrogen as a principal ingredient, and a very small amount, such as only several %, of oxygen as an impurity, and Fe.sub.2 O.sub.3 having a large amount, such as several tens %, of oxygen as a principal ingredient, and a very small amount of nitrogen as an impurity. To date there is no analyzer meeting such a requirement, so that to make such an analysis it has been necessary to use the above described gas analyzer having a conventional constrution for simultaneously measuring the ingredients.
In such a case it is necessary in order to measure the high-concentration ingredient gas corresponding to the principal ingredients to sample a very small size sample, for example 1 to 2 mg or to greatly dilute the sample gas obtained from a suitable amount of sample material. Accordingly, problems have occurred in that errors of measurement in the measurement of the weight of the sample are relatively increased and influence of the segregations within the sample is inevitable, so that the analytical accuracy is reduced. Further, since the concentration of the ingredient gas corresponding to the impurities is very low, the accuracy of the measurement of the impurities is greatly reduced.
Moreover, with the conventional gas analyzer for simultaneously measuring many ingredients, the problem has occurred in that since the first gas concentration detector 0D.sub.1 and the second gas concentration detector 0D.sub.2 are arranged in series, fundamentally speaking, errors of measurement due to an increase of sensitivity resulting from back pressure from gas concentration detector 0D.sub.2 are liable to appear in the first gas concentration detector 0D.sub.1. Also the problem has occurred that in particular, as shown in said FIG. 6, in the case where a heat conductivity type detector having no selectivity for the gas being analyzed is used as the second gas concentration detector 0D.sub.2, it is necessary to provide to oxidizer 06, the CO.sub.2 -remover 07, the H.sub.2 O-remover 08 and the like between the first gas concentration detector 0D.sub.1 and the second has concentation detector 0D.sub.2, so that the influence of the back pressure upon the first gas concentration detector 0D.sub.1 is gradually increased principally due to progressive clogging of the CO.sub.2 -remover 07 with the passage of time, whereby errors of measurement due to an increase of sensitvity in the first gas concentration detector 0D.sub.1 are increased with the passage of time.